8 ms·
Note: this was implemented without referencing any ZFS source code and should not be subject to the CDDL.
by lunixbochs 7y ago
Note: this was implemented without referencing any ZFS source code and should not be subject to the CDDL.
- josteink 7y agoSo we port this python to something not slow, and all the kernel-people can shut up about ZFS being terrible ;)
- j88439h84 7y agoDont forget, pypy is fast.
- spullara 7y agoFaster that CPython doesn't mean it is fast.
- twa927 7y agoI was trying to speed up a log processing service running on PyPy by rewriting it in Java. I was surprised that the result was about twice slower (I know Java quite well and I didn't see obvious optimizations; most of the time was spent in GC). So it can be quite fast even in more absolute terms (VM languages), at least for some types of code.
- spullara 7y agoIf more than 1% of your time is in GC you are doing something very wrong.
- tigershark 7y agoI know that it’s asking a lot, but any chance that you can post a minimum reproducible sample? From what I know it is quite smelly...
- twa927 7y agoI don't have access to this codebase now but I'll try to write some benchmark.
- tigershark 7y agoIf you manage to do it would be awesome, otherwise thanks a lot anyway for the effort :) I’m just curious to understand why it happens because it’s exactly the opposite of what I would expect. The only explanation that comes to my mind is excessive gc as someone else already mentioned, but it would be interesting to see the original code.
- twa927 7y agoI started doing it but yes, it's too much effort to get two full benchmarks, I'm sorry :). But I think it went down to the inefficiency of String.split(): https://stackoverflow.com/questions/37007189/string-split-temporary-objects-and-garbage-collect https://stackoverflow.com/questions/37007189/string-split-te... and generally the Java's String built-in methods not being GC-friendly: https://stackoverflow.com/questions/20336459/garbage-friendly-alternative-to-substring https://stackoverflow.com/questions/20336459/garbage-friendl.... I'm guessing that when such parts can be coded in a non-VM environment (CPython/PyPy runtime) they can be made much faster, and Java to these days has the standard library coded in pure Java?
- auscompgeek 7y agoCPython and PyPy are both VMs, similarly to the JVM.
- twa927 7y agoI meant the inside of a VM (its implementation), which is coded in C/RPython. Java's VM is coded in C++, but I don't think C++ is used for any regular library functions, while C is used heavily for Python's stdlib.
- deleted 7y ago[deleted]
- michaelmrose 7y agoThe fact that a singular implementation was better than java says less about the languages and more about the particular software.
- d0mine 7y agoI would have expected it: https://stackoverflow.com/questions/9371238/why-is-reading-lines-from-stdin-much-slower-in-c-than-python https://stackoverflow.com/questions/9371238/why-is-reading-l...
- int_19h 7y agoI had a binary parser written in Python that took around 30 seconds on typical input on CPython. PyPy took that down to about 10 seconds. Rewriting it in C# took it down to 200 ms.
- twa927 7y agoIf this was using a loop processing a single byte in an iteration I would expect a greater speedup on PyPy. I've seen 100x speedup in such cases.
- int_19h 7y agoNot single byte, but individual fields (float32/int32/string etc). Yes, I expected a much more significant speed-up as well. It's probably because a lot of that code was driven by reflection-type techniques. Curiously, IronPython did better than anything (but still slow). Haven't tried Jython. Compiling the whole thing with Cython was less effective than PyPy.
- twa927 7y agoYes, reflection voids many JIT paths in PyPy, AFAIK. Maybe it was worth rewriting the Python code to get rid of the reflection?
- cure 7y agoPyPy is faster than Python, yes. But Go, C and many other (compiled) languages are way faster than PyPy. Plus, if you use a language like Go or Rust then you avoid Python's GIL and you'll have much more reasonable memory usage. Best of all, deploying is a matter of copying a binary, rather than having to deal with the absolute disaster that is Python packaging.
- klyrs 7y agoFilesystem with a GIL, what could possibly go wrong? /s
- emmelaich 7y agoA lot less will go wrong than a filesystem without a GIL. GIL is for safety and correctness, not speed.
- y4mi 7y agoUh, no? Python's global interpreter lock was added for single threaded speed and c library integrations, which often can't be used multithreaded There was some talk about removing it recentlish to improve pythons multithreaded performance and Guido said something along the lines of > "I'll remove it as long as single threaded performance doesn't suffer" Which nobody succeeded in
- nine_k 7y agoGo? A GC'd language in kernel? (Well, yes, this has been done, from Lua to Haskell, but only experimentally.)
- tanilama 7y agoOnly when comparing to CPython
- fragmede 7y agopypy is fast, but even were this written in C, there's still the kernel-userland boundary to contend with.
- moonbug 7y agoFuse
- yjftsjthsd-h 7y agoIf you're going to run the file system in user space, there's no reason not to just use normal ZFS. The problem with ZFS licensing is only in combining CDDL+GPL in one unit. If you're working across the kernel/userspace boundary, there's already no problem. ZoL even already ships a fuse version that works fine.
- Conan_Kudo 7y ago> ZoL even already ships a fuse version that works fine. This is not true. A FUSE implementation is wanted though: https://github.com/zfsonlinux/zfs/issues/8 https://github.com/zfsonlinux/zfs/issues/8
- yjftsjthsd-h 7y agoOops; I didn't realize the existing fuse version wasn't built from ZoL. Thanks for pointing that out.
- GuB-42 7y agoMaybe plenty fast for most applications but a filesystem is not one of these IMHO, especially for something as naturally resource hungry as ZFS. A good filesystem implementation requires tight memory management and good control of what happens at the OS level. I am not saying it can't be be done in python, but it clearly isn't the right tool for the job. I meant that for a production implementation. Python is perfectly fine for a proof of concept, in fact, it may be better than jumping straight down to C. But keeping it for production is foolish IMHO.
- mehrdadn 7y agoI routinely fail to get speedup on PyPy. In fact I frequently get slowdowns. I imagine it's only fast if your code is slower than it needs to be to begin with.
- twa927 7y agoIt works well for tight loops processing much data, or heavy object-orientation (multiple levels of class hierarchies). It probably won't work well for regular Django webapps or scripts. Also, real-world Python numerical/AI code uses numpy/ML libs so there's not much to optimize in Python...
- aidenn0 7y agoI can Port from Python -> Common Lisp at a rate of ~100 LoC per hour, and that's a pretty friendly port (the yield expression is the only thing that can't be just done line-by-line; truthyness is the only real "gotcha" as there are a lot of "false" values in Python, but only 1.5 in Lisp[1]). 1: I say 1.5 because there is only one false value, but it has 2 idiomatic meanings: nil (equivalent to python's None) and the empty list.
- newnewpdro 7y agoWould the CDDL matter for a python implementation that will never become part of the kernel?
- dr0verride 7y agoIt's clear to me that the solution is to integrate python into the kernel.
- yjftsjthsd-h 7y agoI assume you mean this as a joke, but I would point out that at least one of the BSD family has gone and baked lua into their kernel. Granted, lua is rather meant for that kind of thing and python isn't, but it is entertaining to point out an interpreted language that has been stuck into a unix kernel:)
- riffraff 7y agothere was lua in linux too, with lunatik https://github.com/lunatik-ng/lunatik-ng https://github.com/lunatik-ng/lunatik-ng
- CaliforniaKarl 7y agoYou'd want a reverse-engineering lawyer, so be certain. But my (IANAL) guess is: If this is a proper reverse-engineered implementation, you could then convert _this_ implementation to C, and contribute _that_ into the kernel. Except, it seems this is BSD-licensed, so I'm not sure how that would work in the kernel (which is GPLv2).
- lunixbochs 7y agoBSD is a subset of GPL's restrictions, so you can include BSD-licensed code in a GPL work.
- loeg 7y ago
- lelf 7y agoBad title. It’s not a ZFS implementation, so hold your horses.
- AHTERIX5000 7y agoWhat do you mean? Can't you mount & read ZFS filesystems with this one?
- Annatar 7y agoCDDL isn't a fascist license like GPL, so there is no penalty for looking at the source code licensed under CDDL. Let's leave the GPL ideology out of this.